High-precision punch and die method

ABSTRACT

A high-precision punch and die method wherein a pair of pneumostatic bearings are mounted on a rigid frame structure in registered spaced-apart relation to each other, each bearing having a plurality of journal segments provided with a pneumostatic bearing surface and adjustably mounted on the frame structure. A segmented die is mounted on the frame structure in registered spaced-apart relation to (and preferably between) the two bearings, the die having a plurality of die segments provided with a cutting edge and adjustably mounted on the frame structure. The bearing journal segments and the die segments are adjusted, by use of a mating set-up bar, to achieve required sizing and alignment of the bearings and die. A punch is then positioned in the bearings for guided movement through the die, the punch having an integral pneumostatic bearing surface closely facing each journal-segment bearing surface and a cutting edge adapted to coact with each die-segment cutting edge. A pressurized gas, preferably air, is controllably supplied to each journal-segment bearing surface to provide needed constraint and guidance to the punch. The punch is then moved, as by a pneumatic cylinder, through the bearings and die to bring the punch and die cutting edges into precise coaction.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to punch and die processes, andparticularly to such a process that provides the combined advantages ofhigh precision and low tool wear.

2. Description of the Prior Art

The prior art is replete with disclosures of various apparatus andmethods intended to achieve precisely controlled positioning of a movingmember. For example, U.S. Pat. No. 3,903,993 to Vorrhees et al.discloses a press slide which is reciprocable in a press frame.Hydrostatic bearings guide the slide as it reciprocates, and they resistany lateral deflection thereof due to an unbalanced load. For anotherexample, U.S. Pat. No. 4,448,460 to Yamamoto discloses a hydrostaticbearing arrangement intended to achieve greater load bearing capacityand rigidity for a sliding member. Also, U.S. Pat. No. 4,606,587 toThompson discloses a precision air slide that includes a slide ram whichis movable, with the aid of air bearings, inside a relatively stationarysegmented housing.

While such known apparatus and methods may have sufficed for theirrespective purposes, there has remained a persistent need for aneffective and practical way to achieve both high precision andnegligible tool wear in a punch and die process.

SUMMARY OF THE INVENTION

Accordingly, a primary object of this invention has been to meet theforegoing need, and to do so in a totally reliable, yet practical andeconomical, manner. That and other objects have been achieved by theinvention herein disclosed and claimed.

This invention finds utility in a high-precision punch and die methodcomprising the steps of (a) providing a rigid mounting frame structure;(b) mounting on the frame structure a pair of pneumostatic bearings inregistered spaced-apart relation to each other, the bearings each havinga plurality of bearing journal segments provided with a pneumostaticbearing surface and adjustably mountable on said structure, the bearingmounting step including adjustably mounting the journal segments of bothbearings on said structure; (c) mounting on the frame structure asegmented die in registered spaced-apart relation to the bearings, thedie having a plurality of die segments provided with a cutting edge andadjustably mountable on said structure, the die mounting step includingadjustably mounting the die segments on said structure; (d) adjustingthe journal segments and the die segments so as to achieve requiredsizing and alignment of the bearings and the die; (e) positioning in thebearings a punch adapted for guided movement through the bearings andthe die, the punch having integral pneumostatic bearing surfaces and atleast one cutting edge, the punch positioning step including positioningthe punch between the journal segments of each bearing so that thebearing surface on each journal segment is in close face-to-facerelation to an opposing one of the bearing surfaces on the punch, and sothat the cutting edge(s) on the punch is (are) disposed in coactablerelation to the cutting edge on each of the die segments; (f)controllably supplying a pressurized gas to the bearing surface on eachof the journal segments to provide required constraint and guidance tothe punch; and (g) effecting movement of the punch through the bearingsand the die so as to move the cutting edge(s) on the punch into coactingrelation with the cutting edge on each of the die segments.

This invention, and its objects and advantages, will become moreapparent in the detailed description of the illustrated embodimentsthereof presented hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

In the detailed description of the embodiments of this inventionpresented below, reference is made to the accompanying drawings, whereinlike reference characters denote like elements, and wherein:

FIG. 1 is a perspective view of a punch as configured in accordance withan embodiment of this invention;

FIG. 2 is a perspective view of the punch shown in FIG. 1 together witha segmented die configured in accordance with an embodiment of thisinvention;

FIG. 3 is a perspective view of the punch and die shown in FIG. 2together with a pair of pneumostatic bearings configured in accordancewith an embodiment of this invention;

FIG. 4 is a perspective view similar to FIG. 3 but with additionalstructure for mounting the die and pneumostatic bearings, and withschematic depiction of respective means for pressurizing the bearingsand moving the punch therethrough;

FIG. 5 is a perspective view similar to FIG. 4 but showing an exemplarywork piece still in place after being notched by the punch and die;

FIG. 6 is a perspective view of a set-up bar useful in correctly sizingand aligning the bearings and die shown in FIGS. 3-5; and

FIGS. 7-10 are perspective views illustrating alternative embodiments ofthe present invention.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Because certain parts of, and practices relating to, punch and dieapparatus and methods are well known, the following description isdirected in particular to those elements and steps forming orcooperating directly with this invention. Elements and steps notspecifically shown or described herein are selectable from those knownin the relevant art.

FIG. 1 illustrates a punch 10 configured in accordance with oneembodiment of this invention. Punch 10 is an elongate one-piece membermade of air-hardened tool steel and having a generally rectangular crosssection. Punch 10 has a cut-out section 12 with a cutting edge 14 formedat the upper end thereof. Above and below cut-out section 12, on allfour sides of the punch, are integral pneumostatic bearing surfaces,only four of which, 16, 18, 20, and 22, are shown. At the top end ofpunch 10 are a pair of lugs 24 adapted to be operatively coupled to asuitable motion-imparting means such as a pneumatic cylinder.

Turning now to FIG. 2, punch 10 is shown together with a segmented dye26, which comprises three die segments 26a, 26b, and 26c having cuttingedges 28a, 28b, and 28c, respectively. The die segments are clusteredabout a central portion of cut-out section 12 so as to position theircutting edges for proper coaction with cutting edge 14, to effectthereby a desired cutting action upon downward movement of the punchthrough the die. The generally U-shaped die 26 is segmented as shown sothat each leg of the U individually may be machined to the precisionrequired, sharpened, and adjustably set to achieve a "near zero"clearance with the opposing surface of punch 10. The die segments alsoare made from air-hardened tool steel.

FIG. 3 shows the punch and die combination of FIG. 2 together withsegmented upper and lower pneumostatic bearings 30 and 34. Upper bearing30 comprises bearing segments 30a, 30b, 30c, and 30d provided withpneumostatic bearing surfaces 32a, 32b, 32c, and 32d respectively.Similarly, lower bearing 34 comprises bearing segments 34a, 34b, 34c,and 34d provided with pneumostatic bearing surfaces 36a, 36b, 36c, and36d respectively. Both bearings 30 and 34 are positioned so that theirbearing surfaces lie in close face-to-face relation to respective onesof the bearing surfaces on punch 10. For example, upper bearing surface32b lies in close facing relation to punch bearing surface 16, whileupper bearing surface 32c lies in such relation to punch surface 18.Similarly, lower bearing surfaces 36b and 36c lie in such relation topunch bearing surfaces 20 and 22 respectively.

FIG. 4 illustrates the combination just described mounted to astationary, rigid, mounting frame structure 40. In this figure, three ofthe lower bearing segments are shown extended in a U-shaped manner toprovide corresponding integral supports for the die segments. Thus,bearing segment 34a as so extended includes a horizontal leg 38a forsupporting die segment 26a. Similarly, bearing segment 34b as extendedincludes a horizontal leg 38b for supporting die segment 26b, andbearing segment 34c as extended includes a horizontal leg 38c forsupporting die segment 26c. Each of the die segments 26a, 26b, and 26cis adjustably mounted on its respective supporting leg by mountingscrews 26s in oversized mounting screw holes. The mounting framestructure 40 comprises a tubular steel structure of rectangular crosssection including four mutually perpendicular walls 40a, 40b, 40c, and40d. Upper bearing segment 30d and lower bearing segment 34d are rigidlysecured to wall 40d. Similarly, upper bearing segment 30c and extendedlower bearing segment 34c are rigidly secured to wall 40c. Upper bearingsegment 30c also is secured to the adjacent end of upper bearing segment30d, and lower bearing segment 34c is secured to the adjacent end oflower bearing segment 34d. Upper bearing segment 30a then is adjustablymounted to the adjacent end of upper bearing segment 30b, which isadjustably mounted to the adjacent end of upper bearing segment 30c.Similarly, lower bearing segment 34a and supporting leg 38a areadjustably mounted to the adjacent ends of lower bearing segment 34b andsupporting leg 38b respectively. FIG. 4 shows the foregoing members somounted upon structure 40 with punch 10 inserted through the openingsthus provided by the air bearings and die.

Also depicted in FIG. 4 are upper bearing gas supply ports 30g and lowerbearing gas supply ports 34g. Preferably, for convenience, the gassupplied through those ports to their respective bearing surfaces isair. Ports 30g and 34g are schematically shown connected throughsuitable control means C30 and C34 to a source G of pressurized air.Also schematically shown in this figure is a pneumatic cylinder P,operatively coupled to lugs 24 at the top end of punch 10, for effectingmovement of the punch through the die as required for a desired cuttingoperation.

FIG. 5 is similar to FIG. 4 in that it shows the principal components ofthe punch and die apparatus just described, but also shows a rectangularwork piece K still in its work position after a notch N has been cut inone edge thereof.

FIG. 6 illustrates a set-up bar B that is used in setting up thedescribed apparatus to achieve the required sizing and alignment of itspneumostatic bearings and die. As may be seen from a comparison of FIGS.1 and 6, bar B is similar to punch 10 without cut-out section 12 andlugs 24. Bar B is made slightly wider and thicker than punch 10 in orderto achieve the clearances needed between the punch and the bearings anddie. In setting up the apparatus, bar B is positioned in the bearing anddie openings, and the adjustably mounted bearing and die segments arethen set in contact with the opposing surfaces on the bar. The mountingscrews for those segments are then tightened, and the bar is removed. Inthis manner, the bearings and die are precisely aligned with oneanother, and they are sized to provide the working clearances neededbetween them and the punch. The punch is then inserted through thebearing and die openings and operatively coupled to the aforementionedpneumatic cylinder P.

FIG. 7 illustrates an alternative embodiment of the present invention.Shown in this figure is a punch 50 which is similar to punch 10 butdiffers therefrom in that cut-out section 52 of punch 50 is configuredto provide a rectangular punch finger 54 having four orthogonal cuttingedges 56. Adjustably mounted for alignment with punch finger 54 is asegmented die 58 comprising four die segments 58a, 58b, 58c, and 58d.Those segments have cutting edges 60a, 60b, 60c, and 60d which coactwith punch finger cutting edges 56 to cut a rectangular aperture. Punch50 is provided with pneumostatic bearing surfaces above and below die 58for cooperation with pneumostatic bearings similar to those describedabove.

FIG. 8 depicts another embodiment of this invention wherein punch 70has, within its cut-out section 72, a depending cylindrical punch finger74 with a circular cutting edge 74e. For convenience, finger 74 may bemade removable from the punch. In this embodiment, the cooperating die76 is a non-segmented, one-piece die provided with a cylindrical dieopening 76o having a circular cutting edge 76e that coacts with punchfinger cutting edge 74e to cut a circular aperture. Here too, the punchis constrained and guided by pneumostatic bearings disposed above andbelow the die.

FIG. 9 illustrates still another embodiment, which is similar to thatshown in FIG. 3 but differs therefrom in that die 26' in FIG. 9 isdisposed below both pneumostatic bearings 30' and 34'. In thisembodiment, punch 80 has its cut-out section 82 and cutting edge 84located at the bottom end of the punch to cooperate with the die 26'below lower bearing 34'.

FIG. 10 depicts yet another embodiment, which is similar to that shownin FIG. 9 but differs therefrom in that punch 90 in FIG. 10 has,depending from its bottom end, a cylindrical punch finger 92 with acircular cutting edge 92e disposed above a cooperating one-piece die 76'having a cylindrical die opening 76o' and circular cutting edge 76e'. Asin the FIG. 8 embodiment, finger 92 may be removable from punch 90 forconvenience in sharpening and replacement.

From all of the foregoing, it will be seen that this invention isadaptable for use in various ways to meet a variety of needs in punchand die processes. Such a process as improved by this invention hasproven successful in high-volume production applications requiringextremely precise punch constraint and guidance, very little tool wear,and facile set-up and change-over capability.

The present invention has now been described in detail with particularreference to embodiments illustrated herein. It will be understood,however, that variations and modifications can be effected within thespirit and scope of this invention.

I claim:
 1. A high-precision punch and die method comprising the stepsof:(a) providing a rigid mounting frame structure; (b) mounting on saidframe structure a pair of pneumostatic bearings in registeredspaced-apart relation to each other, said bearings each having aplurality of bearing journal segments provided with a pneumostaticbearing surface and adjustably mountable on said structure, said bearingmounting step including adjustably mounting said journal segments ofboth bearings on said structure; (c) mounting on said frame structure asegmented die in registered spaced-apart relation to said bearings, saiddie having a plurality of die segments provided with a cutting edge andadjustably mountable on said structure, said die mounting step includingadjustably mounting said die segments on said structure; (d) adjustingsaid journal segments and said die segments so as to achieve requiredsizing and alignment of said bearings and said die; (e) positioning insaid bearings a punch adapted for guided movement through said bearingsand said die, said punch having integral pneumostatic bearing surfacesand at least one cutting edge, said punch positioning step includingpositioning said punch between said journal segments of each bearing sothat said bearing surface on each journal segment is in closeface-to-face relation to an opposing one of said bearing surfaces onsaid punch, and so that said at least one cutting edge on said punch isdisposed in coactable relation to said cutting edge on each of said diesegments; (f) controllably supplying a pressurized gas to said bearingsurface on each of said journal segments to provide required constraintand guidance to said punch; and (g) effecting movement of said punchthrough said bearings and said die so as to move said at least onecutting edge on said punch into coacting relation with said cutting edgeon each of said die segments.
 2. A punch and die method as claimed inclaim 1 wherein said bearing mounting step further includes mountingsaid bearings on said structure so that one of said bearings lies insuperposed spaced-apart relation to the other for vertical alignmentwith said die.
 3. A punch and die method as claimed in claim 2 whereinsaid die mounting step further includes mounting said die on saidstructure between said bearings, whereby said one bearing lies above andsaid other lies below said die.
 4. A punch and die method as claimed inclaim 1 wherein said die mounting step further includes mounting saiddie on said structure between said bearings, whereby said bearings arerespectively disposed at opposite sides of said die.
 5. A punch and diemethod as claimed in claim 1 wherein said adjusting step includespositioning in said bearings and said die a mating set-up bar configuredand dimensioned to provide said required sizing and alignment when saidjournal segments and said die segments are set in contact with said bar,said adjusting step further including so setting said segments and thenremoving said bar.
 6. A punch and die method as claimed in claim 1wherein said gas is air, said pneumostatic bearings are air bearings,and said pneumostatic bearing surfaces are air bearing surfaces; andwherein said gas supplying step includes controllably supplyingpressurized air to said bearing surface on each of said journalsegments.
 7. A punch and die method as claimed in claim 1 wherein saidmovement effecting step includes actuating a pneumatic cylinderoperatively coupled to said punch.